Self restrained joint for ductile iron pipe and fittings

Abstract

A combination sealing and restraint system for an as-cast ductile iron pipe systems. A ductile iron pipe/fitting with a bell end has an as-cast profile formed therein for receiving both a gripping ring and a sealing ring in spaced apart locations. The gripping ring is installed within a first recess provided as a part of the as-cast profile in a post-casting step. The sealing ring is also installed within a second, spaced recess after the casting operation is complete. The sealing ring can be a dual durometer gasket which can be flexed and inserted into the profile. The same type bell end can be provided as an adapter which converts a traditional mechanical joint restraint to an internal gripping and restrain system.

1 . A combination sealing and restraint system for installation within an as-cast profile provided within a mouth region located adjacent an end opening of a body of an as-cast ductile iron pipe/fitting capable of both sealing and restraining the ductile iron pipe/fitting to a mating male pipe having an interior surface and an exterior surface, the sealing and restraint system comprising:
 a gripping ring installed within a first recess provided as a part of the as-cast profile of the ductile iron pipe/fitting, the gripping ring being installed in a post-casting step, the gripping ring having an inner circumferential surface and an outer circumferential surface, the inner circumferential surface having at least one row of teeth located thereon for engaging selected points on the exterior surface of the mating male pipe; and   a sealing gasket having an annular gasket body at least a portion of which is made of a resilient elastomeric material, the annular gasket body having an inner circumferential region and an outer circumferential region, the sealing gasket being installed within a second spaced recess provided as a part of the as-cast profile within the mouth region of the ductile iron pipe/fitting so that the outer circumferential region forms a seal with the fitting mouth region and the inner circumferential region forms a sealing surface for a mating male pipe section, the sealing gasket being installed within the second spaced recess in a post-casting step after forming the pipe/fitting body.   
   
   
       2 . The combination sealing and restraint system of  claim 1 , wherein the sealing gasket is a dual durometer gasket. 
   
   
       3 . The combination sealing and restraint system of  claim 1 , wherein the gripping ring is formed of metal which has been coated with a low-coefficient of friction coating. 
   
   
       4 . The combination sealing and restraint system of  claim 3 , wherein the coating is a first layer of aan aqueous phenolic resin dispersion, which is then covered with a fluoroelastomer top coat. 
   
   
       5 . The combination sealing and restraint system of  claim 1 , wherein the gripping ring is a single piece ring which has a slit at one circumferential location which creates at least one gap, the gap being defined between two opposing faces of the gripping ring when the ring is in a relaxed state, the gap being sufficient to allow the gripping ring to be placed on a die or tool during the casting operation. 
   
   
       6 . The combination sealing and restraint system of  claim 1 , wherein the mating male pipe which is used with the restraint system of the invention is also made from iron. 
   
   
       7 . The combination sealing and restraint system of  claim 1 , wherein the mating male pipe which is used with the restraint system of the invention is made from a plastic material. 
   
   
       8 . The combination sealing and restraint system of  claim 1 , wherein the sealing gasket which is used with the restraint system of the invention is a snap-fit gasket having an embedded reinforcing ring which is not easily bent or flexed by hand and which is of a diameter which is generally greater than the diameter of the mouth opening of the as-cast pipe/fitting. 
   
   
       9 . The combination sealing and restraint system of  claim 1 , wherein the mating male pipe is formed of iron and wherein the gripping ring is formed of hardened steel which has been heat treated to at least about 370 Brinell hardness (BHN) so that the teeth of the ring can penetrate the mating male iron pipe exterior surface or form a buttress on the pipe surface. 
   
   
       10 . The combination sealing and restraint system of  claim 1 , wherein the sealing gasket is activated by internal hydraulic forces of fluids passing through the pipe/fitting body during use, the hydraulic forces also serving to cause the gripping teeth on the gripping ring to engage the exterior surface of the mating male pipe. 
   
   
       11 . The combination sealing and restraint system of  claim 1 , wherein the pipe/fitting is part of a device selected from the group consisting of hydrant tees and flow line valves. 
   
   
       12 . An adapter for connecting a ductile iron mechanical joint to a mating male pipe section, the adapter comprising:
 a generally cylindrical ductile iron adapter body having an interior surface and an exterior surface, the interior surface including a combination sealing and restraint system which is installed within an as-cast profile provided within a mouth region located adjacent an end opening of the adapter body capable of both sealing and restraining the adapter body to a mating male pipe having an interior surface and an exterior surface;   the cylindrical adapter body having an external flange ring formed thereon as an integral part of the as-cast body of the adapter, the external flange ring having a plurality of bolt openings for receiving joining bolts which are used to join the adapter to a mating mechanical joint having a mating flange ring; and   wherein the sealing and restraint system which is installed within the mouth region of the adapter body includes a gripping ring installed within a first recess provided as a part of the as-cast profile of the adapter body, the gripping ring being installed in a post-casting step, the gripping ring having an inner circumferential surface and an outer circumferential surface, the inner circumferential surface having at least one row of teeth located thereon for engaging selected points on the exterior surface of the mating male pipe; and   a sealing gasket having an annular gasket body at least a portion of which is made of a resilient elastomeric material, the annular gasket body having an inner circumferential region and an outer circumferential region, the sealing gasket being installed within a second spaced recess provided as a part of the as-cast profile within the mouth region of the adapter body so that the outer circumferential region forms a seal with the fitting mouth region and the inner circumferential region forms a sealing surface for a mating male pipe section, the sealing gasket being installed within the second spaced recess in a post-casting step after forming the adapter body.   
   
   
       13 . The adapter of  claim 12 , wherein the sealing gasket is a dual durometer gasket. 
   
   
       14 . The adapter of  claim 12 , wherein the gripping ring is a single piece ring which has a slit at one circumferential location which creates at least one gap, the gap being defined between two opposing faces of the gripping ring when the ring is in a relaxed state, the gap being sufficient to allow the gripping ring to be placed on a die or tool during the casting operation. 
   
   
       15 . The adapter of  claim 12 , wherein the mating male pipe which is used with the restraint system of the invention is also made from iron. 
   
   
       16 . The adapter of  claim 12 , wherein the mating male pipe which is used with the restraint system of the invention is made from a plastic material. 
   
   
       17 . The adapter of  claim 12 , wherein the sealing gasket which is used with the restraint system of the invention is a snap-fit gasket having an embedded reinforcing ring which is not easily bent or flexed by hand and which is of a diameter which is generally greater than the diameter of the mouth opening of the as-cast pipe/fitting. 
   
   
       18 . The adapter of  claim 12 , wherein the mating male pipe is formed of iron and wherein the gripping ring is formed of hardened steel which has been heat treated to at least about 370 Brinell hardness (BHN) so that the teeth of the ring can penetrate the mating male iron pipe exterior surface or form a buttress on the pipe surface. 
   
   
       19 . The adapter of  claim 11 , wherein the sealing gasket is activated by internal hydraulic forces of fluids passing through the pipe/fitting body during use, the hydraulic forces serving to cause the gripping teeth on the gripping ring to engage the exterior surface of the mating male pipe. 
   
   
       20 . The adapter of  claim 11 , wherein the pipe/fitting is part of a device selected from the group consisting of hydrant tees and flow line valves. 
   
   
       21 . A method of forming a pipe joint, the method comprising the steps of:
 providing a fluid piping system including at least one as-cast ductile iron pipe/fitting, previously cast at a foundry, having a mouth region adjacent an end opening thereof, the mouth region having an as-cast profile formed therein, the end opening of the pipe/fitting being sized to receive a mating male pipe having an interior surface and an exterior surface;   including a combination sealing and restraint system which is installed within the as-cast profile provided within the mouth region of the pipe/fitting which is capable of both sealing and restraining the pipe/fitting to a mating male pipe having an interior surface and an exterior surface;   wherein the sealing and restraint system which is installed within the mouth region of the pipe/fitting includes a gripping ring installed within a first recess provided as a part of the as-cast profile of the adapter body, the gripping ring being installed in a post-casting step, the gripping ring having an inner circumferential surface and an outer circumferential surface, the inner circumferential surface having at least one row of teeth located thereon for engaging selected points on the exterior surface of the mating male pipe;   wherein the sealing and restraint system also includes a sealing gasket having an annular gasket body at least a portion of which is made of a resilient elastomeric material, the annular gasket body having an inner circumferential region and an outer circumferential region, the sealing gasket being installed within a second spaced recess provided as a part of the as-cast profile within the mouth region of the pipe/fitting so that the outer circumferential region forms a seal with the fitting mouth region and the inner circumferential region forms a sealing surface for a mating male pipe section, the sealing gasket being installed within the second spaced recess in a post-casting step after forming the pipe/fitting; and   thereafter installing a mating male pipe within the end opening of the mouth region of the as-cast pipe/fitting by pushing the male pipe within the end opening, the sealing ring and gripping ring contacting the external surface of the mating male pipe in order to both seal and restrain the mating male pipe and form a secure pipe joint.   
   
   
       22 . The method of  claim 21 , wherein the pipe/fitting comprises a cylindrical adapter body having an external flange ring formed thereon as an integral part of the as-cast body of the adapter, the external flange ring having a plurality of bolt openings for receiving joining bolts which are used to join the adapter to a mating mechanical joint having a mating flange ring. 
   
   
       23 . The method of  claim 22 , wherein the adapter body is bolted to an existing ductile iron mechanical joint and thereafter a mating male pipe end is inserted within the mouth opening of the adapter to form a secure joint.